title: Correlates of average daily metabolism of field-active zebra-tailed lizards (Callisaurus draconoides).
abstract: The extent of variation in reptile field metabolism, and its causal bases, are poorly understood. We studied the energetics of the insectivorous lizard Callisaurus draconoides at a site in the California Desert (Desert Center) and at a site at the southern tip of the Baja Peninsula (Cabo San Lucas; hereafter, Cabo). Reproducing Callisaurus were smaller at Cabo than at Desert Center. The allometry of metabolism with body mass can account for most differences in whole-animal metabolism. There was no significant effect of sex or source population on mass-adjusted metabolic rate in the laboratory (resting metabolism, measured by closed-system respirometry) or in the field (field metabolism, measured with doubly labeled water). The mass-adjusted resting metabolism and field metabolism of gravid females and the field metabolism of juvenile lizards were not significantly different from those of nonreproductive adults. Temperature had a significant effect on resting metabolism (Q10 = 2.7); fed lizards had resting metabolism that was 22% higher than that of fasted lizards; field metabolism was positively correlated with growth rate in juveniles; and field metabolism of adults increased from spring to late summer at Desert Center by 25%, probably because of longer activity period length and slightly higher activity period body temperature. We calculated from water influx and field metabolism that juveniles allocated 18% of their metabolizable energy intake to growth and that most energy deposited into eggs was transferred from energy stores rather than ingested in the weeks prior to laying.
authors.affiliation: Department of Wildlife Ecology, University of Wisconsin, Madison 53706, USA.
authors.forename: W H
authors.initials: WH
authors.lastname: Karasov
authors.forename: R A
authors.initials: RA
authors.lastname: Anderson
mesh_terms: D000375:Aging / Q000378:metabolism / Q000502:physiology; D000818:Animals; D001522:Behavior, Animal / Q000502:physiology; D015992:Body Mass Index; D001831:Body Temperature / Q000502:physiology; D002140:California; D002940:Circadian Rhythm / Q000502:physiology*; D003889:Desert Climate; D004435:Eating / Q000502:physiology; D004734:Energy Metabolism / Q000502:physiology*; D005260:Female; D008116:Lizards / Q000254:growth & development / Q000378:metabolism* / Q000502:physiology; D008297:Male; D010101:Oxygen Consumption / Q000502:physiology; D012098:Reproduction / Q000502:physiology; D012119:Respiration / Q000502:physiology; D012621:Seasons; D013696:Temperature; D013997:Time Factors